The field of the invention is in the smoke and atmospheric particle detection art.
Many types of smoke detecting devices are known. Some simple devices merely utilize the attenuation of a light beam for an indication that smoke or some particulate matter has intercepted the beam. More sophisticated devices use a forward scattering effect measured in a labyrinth. U.S. Pat. No. 3,860,818 to patentees Stalder et al is an example of a typical atmospheric monitor. Some state of the art devices use high power laser beams. They are very satisfactory smoke detectors but generally they are hazardous to personnel.